Picture gallery of common problems

Skin colour
Skin colour is a very important sign of illness.

Redness is a sign of inflammation and people with severe abnormal colour vision do not perceive the colour red. They see red as dark brown, sometimes almost black, which makes it difficult for them to see skin rashes and differentiate a red rash or spot from freckles or other pigmented spots. People with abnormal colour vision often report they cannot see the early redness of sunburn (ref 10).

Can you see the pink rash of rubella on the back of the patient in photo 1? The leg of a man in photo 2 has a red area of early erythema nodosum and a small scar. Can you see them?

In the study by Campbell et al (ref 17) more colour-blind doctors failed to see the abnormal signs in photos 1 and 2 than a control group of doctors with normal colour vision.

Photo 3 is of the fine red rash of scarlet fever and photo 4 shows the red cheeks and the pallor around the mouth (“slapped cheeks, white moustache”), which is also a characteristic of scarlet fever. Can you see this?

Of course there are other cues: if you cannot see the red colour of the inflamed areas you still may be able to detect them because they are darker than the surrounding skin although this may be less obvious especially for patients with dark skin (ref 43). Abnormal skin texture or raised areas in rashes can also aid diagnosis.

Photos 3 and 4 are from commons.wikimedia.org/wiki/image:Scarlet fever
Photographer: Alicia Williams

Skin can be blue, yellow or just pale
Cyanosis. The skin becomes blue when the oxygen saturation of arterial blood falls below 85-90%. Cyanosis is shown in photo 5. Can you see that the hands and feet of the baby are bluish?

It is a pretty important sign to observe but it should not be too great a problem for doctors with abnormal colour vision. People with red-green colour vision deficiency can see blue.

However, there is less colour contrast for people with severe colour vision: for people with normal colour vision there is colour contrast between the pink/red of the body and the blue hands and feet. This will be less marked for those with abnormal colour vision because red is not perceived. More colour-blind doctors failed to see mild cyanosis in one of the photos used in the Campbell et al study (ref 17) compared to the control group of colour-normal doctors.

Jaundice is yellowish discoloration of the skin, sclerae (whites of the eyes) and mucous membranes. It is caused by hyperbilirubinemia (increased levels of bilirubin in the blood) and occurs in liver disease, malaria and when the bile duct is obstructed. Jaundice comes from the French word jaune, meaning yellow.

Detecting jaundice should not be too great a problem for doctors with abnormal colour vision, since yellow is perceived by those with red-green colour vision deficiency. Can you see the yellow colouration in photo 6? Normal skin often looks slightly yellow to those with the deficiency and so does not make a marked contrast when there is jaundice. Jaundice was missed by a greater number of the colour blind doctors compared to a control group of colour normal doctors in the Campbell et al study (ref 17) for one of the three jaundice photos used in the study. They were also significantly less confident of their judgement.

Photo 6 is from wikimedia commons - http://en.wikipedia.org/wiki/
Image: Jaundice2008.jpg

Pallor. People with abnormal colour vision are likely to have problems judging pallor not because they cannot see white but because normal redness is not seen, so the difference between pallor and normal colour is not as great. The pallor of the face in photo 7 is very evident for a doctor with normal colour vision. The doctor with severe abnormal colour vision will find the judgment more difficult.

The ear. The ear can get infected and inflamed. When this occurs behind the ear drum it is called otitis media. Doctors look at the ear with an otoscope and detect the redness and inflammation (ref 40). Photo 8 shows the normal ear drum. Photo 9 is not of otitis media but shows the rare Schwartz sign in which the drum is flamingo pink with small areas that are grey and silvery. This occurs in active otosclerosis. It is an observation that it is hard for a colour vision deficient doctor to make (ref 26).

The eye. Colour blindness presents problems in diagnosing a red eye due to an infection or allergic response of the conjunctiva of the eye (conjunctivitis). Can you see that the eye is red (inflamed) in photo 10 or does it look pretty normal?

Another problem for the colour-blind doctor is distinguishing haemorrhages in the retina of the eye (ref 21). The ophthalmoscope is used to view the interior of the eye by looking through the pupil. The view of the retina when using an ophthalmoscope is shown in Photo 11. In this picture there are some haemorrhages (the red blobs) due to diabetes. This is an early stage of diabetic retinopathy, which if not brought in check will cause serious vision loss. Photo 12 is the same picture but digitally transformed to the colour appearance for a person with a severe red-green colour deficiency. The red colour is lost and the blobs could either be haemorrhages or melanin pigment spots.

While discussing the eye, have look at photo 13. There is something nasty going on. There is a melanoma in the upper left quadrant, which is threatening to both sight and life. It is obvious that something is wrong, but when the picture is transformed to how it is seen by a person with a severe Protan colour deficiency (photo 14) the clinical picture is not so clear cut.

Doctors and optometrists who are colour-blind will also have problems judging the health of the optic nerve head. The optic nerve head is the white area at about 4 o’clock in photos 13 and 14. Its viability can be threatened by a number of diseases including glaucoma, brain tumours and some inherited disorders. Judging the health of the optic nerve head can be very important and the colour-blind observer is handicapped by an inability to perceive the pinkish colour of a healthy optic nerve.

Seeing fresh blood
Seeing fresh blood in vomit and stool is also a problem. It is important to be able to see fresh blood in vomit or stool.

Can you see the fresh blood in the vomit in photo 15?

In photo 15 there are two small areas of fresh blood. These are difficult to see by the colour blind. Most doctors with normal colour vision saw it but only 2 of 22 of those with a deficiency (unpublished finding).

ACKNOWLEDGEMENTS: Thanks for the photographs are due to the following: the National Slide Bank Welcome Trust ; Professor S Lucas of Bacteriology Department, St Thomas’s Hospital, London; T Stannard and A Dyer of Guys and St Thomas’s NHS Trust, London; Photographic Library of Moorfields Eye Hospital, London; St John’s Institute of Dermatology Photographic, Library.

WARNING: This page is not a test of your colour vision, nor should it be the basis for any decision about studying medicine or choice of career path in medicine. It is only meant to be illustrative of the kinds of problems that may be encountered by colour-blind doctors. Regardless of whether you can or cannot see the critical features illustrated in the photos, we recommend you obtain a full diagnosis of your colour vision and advice about its severity and its implications. You should also give careful thought to all the information in this web site before making any decisions.

Home - Tests - More about CVD - Common CVD problems - Picture gallery - Should I study medicine?
Treatment - Tips - Overview - Published papers - Comments - Links - Authors - Site map